The invention concerns a turning-pivoting commutating rotary switch with brush guides for reversing the direction of rotation of a universal electrical motor, preferably for use in hand tool machines or power tools.
Conventionally, a turning-pivoting brush holder with brush guides configured as a turning-pivoting commutating rotary switch for reversing rotational direction features two diametrically opposed stator contacts, each making contact with two diametrically opposing, partially peripheral contact bars at two contact points, which are conducting connected with the two diametrically opposing brush guides. Consequently, upon pivoting, the commutator rotary switch, on the one hand, by the intermittent contact of the contact points, with the stator contacts, the armature coil pole is reversed, and, on the other hand, the brush guides pivot out of the polar plane as a factor of the direction of rotation. The invention relates to such a commutating rotary switch.
According to DE3731079 or DE3943651, such commutating rotary switches have two diametrically opposing stator contacts, wherein structural space is bilaterally required. Such a space is especially tight in hand tools.
According to DE 37 44 488, a switch ring for a universal electrical motor equipped with two separate, diametrically opposing bridge circuit contacts makes contact with a punched grid that is connected with both stator contacts at only one side of the stator. The fixed brush holder can be switched over the bridge circuit contacts for reversal of the direction of rotation. Heavy brush sparking results through the brush guide due to the armature reaction under heavy load, wherein said brush sparking increasing the wear on the brushes. The brush guide is fixed connected with the punched grid and thus unable to pivot out of the polarization plane as a factor of rotational direction. Further, additional intercircuits between the stator contacts and the bridge contacts are required, whereby the switch ring, itself multi-part, must be rotatable.
According to DE 19 521 702, a low voltage d.c. machine has two partially peripheral, rigid pole connection lines arranged on a fixed brush bridge between the brush mountings, wherein at least one pole connection line extends over half of the periphery.